Recent studies indicate that significant inter-individual variation exists at the amino acid sequence level of BER proteins, and that variability presumably exists in the BER capacity of the general population. We have developed assays to determine the extent of inter-individual variation at specific steps of BER, and will elucidate whether variation in BER correlates with disease susceptibility and/or clinical agent responsiveness. Using these assays, we will also assess for age-dependent or gender-specific variation, within the limits of the sample set in hand. The establishment of such techniques, and ultimately a high throughput BER pathway assay presently in design, will be necessary to evaluate the relationship of BER capacity to disease susceptibility among the Baltimore Longitudinal Study of Aging (BLSA) population.[unreadable] [unreadable] Current strategies to eradicate cancer cells rely on the fact that they divide rapidly. Thus, to induce cell death, many anti-cancer agents interact with DNA to block replication and prevent duplication. Not surprisingly, cells with efficient repair of the cytotoxic DNA intermediates/lesions generated by anti-cancer agents are more resistant to cell killing. Hence, a goal has been to regulate strategically the repair capacity of cancer and/or normal cells to improve the efficacy of specific therapeutic paradigms. In particular, inhibiting the DNA repair capacity of cancerous cells has been an area of promising focus. We have identified a mutant form of the human APE1 protein which we have termed ED that enhances cellular sensitivity to a broad range of clinical alkylating agents and nucleoside analogues. We are presently designing adenoviral-based gene therapy systems to determine the effects of ED on modulating cancer cell survival. In addition, we are screening for small molecule, non-covalent chemical inhibitors of the major human abasic endonuclease APE1, with the long term goal of creating high affinity inhibitors with therapeutic value. The establishment of adenoviral and complementary techniques will provide a foundation for more extensive investigations on the potential benefits to regulating cellular DNA repair capacity.